摘要:

IntroductionElectrothermal atomic absorption spectrometry (ETAAS) is one of the most useful techniques for performing metal analysis based on the direct introduction of solid materials. ETAAS requires the injection of discrete portions of the sample (liquid or solid) to be analyzed. Several reviews have been published covering solid sampling1–6referring to the analysis of specific samples6,7or comparing different atomic spectrometry techniques8based on this approach.From the practical point of view, direct solid introduction can generally be divided into two classes: (a) direct introduction of the sample into a graphite furnace9–11and (b) introduction of a solid support containing the analyte immobilized12,13or coprecipitated with a suitable compound.14,15However, when the last procedure is used, the sample must be previously treated in order to prepare it for analysis. This fact is disadvantageous since sample losses and contamination can occur, making the procedure highly dependent on the skill of the analyst. On the other hand, very low detection limits can be achieved because a preconcentration step is carried out, together with matrix simplification, which yields low background signals.Following the second approach, Takada and Koide12determined copper in water samples after analyte sorption onto a cation-exchange resin (Amberlite IR-120B) and subsequent insertion of the loaded resin into the graphite furnace. Copper was determined in the range of 0.01–6 ng ml−1(concentration in solution) by using 6 mg of resin, 50 ml of sample and an equilibration time of 10 min. Under these conditions a characteristic concentration of 2 pg ml−1and an RSD of 6.4% (at 0.04 ng ml−1) were reported.Shida and Matsuzaki13employed an anion-exchange resin (DIAION PA318) to preconcentrate gallium. After the preconcentration step, the loaded resin containing 10–60 ng of Ga (as a Pyrocatechol Violet anionic complex) was filtered with a membrane type filter and directly inserted into the graphite tube to provide a suitable quantification of the analyte. Under the optimized conditions, a detection limit of 3 ng l−1and an RSD of 5% were obtained from five measurements at 30 ng l−1Ga.Among several other resins employed in solid-phase extraction procedures, the use of polyurethane foam (PUF) has increased in the last few years. It has been successfully applied as a polymeric extractant for the preconcentration and separation of inorganic16–21and organic species.22–26However, the direct analysis of this solid loaded with a particular analyte using an ETAAS-based has not yet been described. This work proposes a new methodology for cobalt determination at trace levels in different types of samples (saline waters and biological materials), based on the utilization of PUF as a solid-phase extractor coupled to solid introduction into a graphite cuvette.

ISSN:0267-9477    

DOI:10.1039/b110804m

出版商:RSC    

年代:2001

数据来源: RSC